Image Collection:

Human Anatomy

Picture of the Lungs

The lungs are a pair of spongy, air-filled organs located on either side of the chest (thorax). The trachea (windpipe) conducts inhaled air into the lungs through its tubular branches, called bronchi. The bronchi then divide into smaller and smaller branches (bronchioles), finally becoming microscopic.

The bronchioles eventually end in clusters of microscopic air sacs called alveoli. In the alveoli, oxygen from the air is absorbed into the blood. Carbon dioxide, a waste product of metabolism, travels from the blood to the alveoli, where it can be exhaled. Between the alveoli is a thin layer of cells called the interstitium, which contains blood vessels and cells that help support the alveoli.

The lungs are covered by a thin tissue layer called the pleura. The same kind of thin tissue lines the inside of the chest cavity -- also called pleura. A thin layer of fluid acts as a lubricant allowing the lungs to slip smoothly as they expand and contract with each breath.

Sarcoidosis: Tiny areas of inflammation can affect all organs in the body, with the lungs involved most of the time. The symptoms are usually mild; sarcoidosis is usually found when X-rays are done for other reasons.

Pleural effusion: Fluid builds up in the normally tiny space between the lung and the inside of the chest wall (the pleural space). If large, pleural effusions can cause problems with breathing.

Pleurisy: Inflammation of the lining of the lung (pleura), which often causes pain when breathing in. Autoimmune conditions, infections, or a pulmonary embolism may cause pleurisy.

Bronchiectasis: The airways (bronchi) become inflamed and expand abnormally, usually after repeated infections. Coughing, with large amounts of mucus, is the main symptom of bronchiectasis.

Lymphangioleiomyomatosis (LAM): A rare condition in which cysts form throughout the lungs, causing breathing problems similar to emphysema. LAM occurs almost exclusively in women of childbearing age.

Cystic fibrosis: A genetic condition in which mucus does not clear easily from the airways. The excess mucus causes repeated episodes of bronchitis and pneumonia throughout life.

Interstitial lung disease: A collection of conditions in which the interstitium (lining between the air sacs) becomes diseased. Fibrosis (scarring) of the interstitium eventually results, if the process can't be stopped.

Coccidioidomycosis: A pneumonia caused by Coccidioides, a fungus found in the soil in the southwestern U.S. Most people experience no symptoms, or a flu-like illness with complete recovery.

Histoplasmosis: An infection caused by inhaling Histoplasma capsulatum, a fungus found in the soil in the eastern and central U.S. Most Histoplasma pneumonias are mild, causing only a short-lived cough and flu-like symptoms.

Influenza (flu): An infection by one or more flu viruses causes fever, body aches, and coughing lasting a week or more. Influenza can progress to life-threatening pneumonia, especially in older people with medical problems.

Mesothelioma: A rare form of cancer that forms from the cells lining various organs of the body with the lungs being the most common. Mesothelioma tends to emerge several decades after asbestos exposure.

Pertussis (whooping cough): A highly contagious infection of the airways (bronchi) by Bordetella pertussis, causing persistent cough. A booster vaccine (Tdap) is recommended for adolescents and adults to prevent pertussis.

Pulmonary embolism: A blood clot (usually from a vein in the leg) may break off and travel to the heart, which pumps the clot (embolus) into the lungs. Sudden shortness of breath is the most common symptom of a pulmonary embolism.

Severe acute respiratory syndrome (SARS): A severe pneumonia caused by a specific virus first discovered in Asia in 2002. Worldwide prevention measures seem to have controlled SARS, which has caused no deaths in the U.S.

Pneumothorax: Air in the chest; it occurs when air enters the area around the lung (the pleural space) abnormally. Pneumothorax can be caused by an injury or may happen spontaneously.